Process for making crimped rayon

ABSTRACT

THE PRODUCTION OF RAYON HAVING A HIGH CRIMP FREQUENCY IS ACHIEVED BY ADDING 2,4-BIS-(N-DIMETHYLAMINOMETHYL) 6-METHYLPHENOL TO VISCOSE AND EMPLOYING CONDITIONS NORMALLY USED IN THE PRODUCTION OF HIGH WET MODULUS STAPLE.

United States Patent 3,632,718 PROCESS FOR MAKING CRIMPED RAYON John H. Bethune and Clement A. Tarzi, Hawkesbury, Ontario, Canada, and Michael R. Bolton and Joseph R. Rainville, Monroe, N.Y., assignors to Canadian International Paper Company, Montreal, Quebec, Canada No Drawing. Filed July 30, 1970, Ser. No. 59,738 Int. Cl. D01f 3/12 U.S. Cl. 264-468 6 Claims ABSTRACT OF THE DISCLOSURE The production of rayon having a high crimp frequency is achieved by adding 2,4-bis-'(N-dimethylaminomethyl)- '6-methylphenol to viscose and employing conditions normally used in the production of high wet modulus staple.

The present invention relates to a process for the production of regenerated cellulose filaments and fibers. More particularly, it relates to a process for the production of crimped continuous filament rayon or staple fiber under process conditions normally employed in the production of high wet modulus staple.

The present method of making chemically crimped rayon fibers consists of spinning viscose under unbalanced process conditions resulting in a fiber cross-section with an unsymmetric skin and core. The spinning conditions required to give unsymmetric skin and core until now depended on the ripening index of the viscose, the ionic strength of the spin bath, i.e., sulfuric acid, zinc sulfate and sodium sulfate, and also the temperature of the bath. Unsymmetric skin and core rayon fibers have also been obtained by simultaneously extruding two viscoses of different ripening indexes through the same hole, i.e., conjugate spinning. However, none of the aforementioned processes will produce a crimpable high wet modulus rayon which is commercially competitive.

Therefore, it is an object of the present invention to provide a process for producing a crimpable rayon.

It is another object of the present invention to provide a process for producing a crimpable rayon under high wet modulus conditions.

It has been found that the incorporation of 2,4-bis-(N- dimethylaminomethyl) 6-methylphenol, as a viscose additive, and the maintenance of carefully controlled viscose and spinning conditions, results in a fiber with a very high crimp frequency, and one whose tenacity, elongation and wet initial modulus is of an intermediate nature. This rayon can be employed in the manufacture of textiles.

The combination of the particular viscose composition and the viscose additive, to be discussed in a more detailed fashion hereinafter, produces fibers having unbalanced cross-sections.

In the production of regenerated cellulosic structures, i.e., rayon filaments, a variety of pulps can be used. Examples thereof are prehydrolyzed kraft pulps, sulfite pulps, cotton linters, etc.

The cellulose of the pulp is converted to alkali cellulose by steeping in from about 16% to about 21%, by weight, of sodium hydroxide for from about 20 minutes to about 60 minutes. The alkali cellulose is then shredded, aged at a temperature of from about C. to about 35 C. and xanthated with from about 30% to about 45% carbon-disulfide.

A typical viscose composition for use in the practice of the present invention contains from about 5% toabout of cellulose, preferably, however, from about 7% to about 8%, and from about 4% to about 9% sodium Patented Jan. 4, 1972 "ice hydroxide, preferably, however, from about 6% to about 8%. All percentages are based upon weight of cellulose in viscose.

A Viscose, as described above, having a salt index of from about 5 to about 10, and preferably between 7.5 and 9.5, and containing from about 1% to about 5%, by weight, of 2,4-bis-(N dimethylaminomethyl)-6-methylphenol, the additive of the present invention, is extruded through a spinnerette into a spin bath, i.e., coagulating and regenerating bath, containing from about 6.0% to about 8.0% sulfuric acid, from about 1.5% to about 5.0% zinc sulfate and from about 9.5% to about 14.0% sodium sulfate. The temperature of the spin bath can be from about 25 C. to about 45 C. and preferably is 35 C.

The additive can be employed in amounts greater than 5 however, it is economically unsound to do so. It is preferred to employ from about 3% to about 4% of the additive, based on the weight of cellulose.

The incompletely regenerated filaments after emerging from the spin bath are stretched between two godets while immersed in a second bath, which is called the stretch bath. The amount of stretch that can be applied can be from about 40% to about 120%, with from about 60% to about 100% stretch being preferred. The stretch bath can contain from about 1% to about 2% sulfuric acid and from about 0.5% to about 1.5 zinc sulfate. The bath is maintained at a temperature of at least C. or above.

After exiting from the stretch bath, the yarn or tow is brought to a staple fiber cutter for cutting and completing regeneration with a mild hot acid wash to produce a crimped staple fiber, or it can be processed through a third bath containing sulfuric acid at 60 C. with practically no relaxation and then washed on self-advancing rubber reels. The yarn is lubricated in a finish trough and dried under practically no tension.

EXAMPLE 1 Tyrecell C, a prehydrolyzed kraft pulp of high rayon cellulose content, produced by International Paper Company, was steeped in a conventional press in 18.0% NaOH for 30 minutes and pressed to a press weight ratio of 2.90 on bone dry cellulose. The alkali cellulose was shredded for 60 minutes, aged overnight at 27 C. and xanthated in a dry churn with 37% CS based on the weight of the cellulose. A viscose of 7.8% cellulose and 7.0% NaOH was prepared. 4% of 2,4 bis ("N-dimethylaminomethyl)- 6- methylphenol based on the weight of the cellulose, was added during mixing of the viscose. The viscose was filtered and deaerated. Ripening was carried out overnight at 10 C., to give a salt index of 7.5. The viscose was spun on a continuous spinning machine into a spinning bath containing 6.2% sulfuric acid, 4.1% zinc sulfate and 12.4% sodium sulfate. The temperature of the bath was 35 C. with a yarn immersion of 21 inches. The spinning speed was 25 meters/minute. The second bath or stretch bath contained 1.1% sulfuric acid and 0.8% zinc sulfate at C., and the godet stretch was 80%. The third bath contained 5.5% sulfuric acid at 60 C. with an irn mersion of 60 inches.

Yarn conditioned tenacity was 2.2 g./ d. with an elongation of 15%. Yarn wet tenacity was 1.9 g./d. with an elongation of 20%. The yarn had as many as 39 crimps/inch with an average of 24. Filament denier was 1.8..

EXAMPLE 2 Tyrecell C pulp was steeped, pressed and shredded in accordance with the procedure in Example 1. Xanthation was carried out with 40% CS based on the weight of the cellulose. A viscose of 7% cellulose and 8% NaOH was prepared. 4% of 2,4-bis-(N-dimethylaminomethyl)-6- methylphenol, based on the weight of the cellulose, was added during mixing of the viscose. The viscose was filtered and deaerated and ripened overnight at 10 C. to give a salt index of 9.5. The viscose was spun on a continuous spinning machine into a spinning bath containing 6.8% sulfuric acid, 2.5% zinc sulfate and 11.0% sodium sulfate. The temperature of the bath was 30 C. with a yarn immersion of 21 inches. The spinning speed was 25 meters/minute. The second and third baths were of the same composition as in Example 1. Stretch to the second godet was 110%120%.

Yarn conditioned tenacity was 4.5 g./d. with an elongation of 13.0%. Yarn wet tenacity was 3.1 g./d. with an elongation of 15%. Yarn wet initial modulus was 12 g./d. (at strain). The yarn had 5-10 crimps/inch. Filament denier was 1.8.

What is claimed is:

1. A process for producing crimped viscose rayon filaments and fibers which comprises extruding a viscose containing from about 5% to about by weight of cellulose, from 4% to about 9% by weight of sodium hydroxide, from about 1% to about 5% by weight of 2,4-bis- (N- dimethylaminomethyl)-6-methylphenol and having a salt index of the viscose is from about 7.5 to about 9.5. containing from about 6% to about 8.0% of sulfuric acid, from about 1.5% to about 5.0% of zinc sulfate and from about 9.5% to about 14.0% of sodium sulfate and having a temperatre of from about 25 C. to about 45 C. to form incompletely regenerated filaments, and then stretching the filaments from about 40% to about 120% while immersed in a dilute sulfuric acid bath maintained at a temperature of C. or above, and then completing the regeneration of the filaments.

2. The process as recited in claim 1 wherein from about 3% to about 4%, by weight, of 2,4-bis-(N-dimethylaminomethyl)-6-methylphenol is employed.

3. The process as recited in claim 1 wherein the cellulose content of the viscose is from about 7% to about 8% by weight.

4. The process as recited in claim 1 wherein the sodium hydroxide content is from about 6% to about 8%, by weight.

5. The process as recited in claim 1 wherein the salt index of the viscose is from about 7.5 to about 9.5.

6. The process as recited in claim 1 wherein the filaments are stretched from about 60% to about while immersed in the dilute sulfuric acid bath.

References Cited UNITED STATES PATENTS 3,277,226 10/1966 Bockno et al. 264-188 3,494,996 2/ 1970 Stevens et al. 264-497 3,388,117 6/1968 Roberts et al. 264-197 JAY H. WOO, Primary Examiner U.S.Cl.X.R.

106--l65, 189; 264l9l, 194 

